3D scanning

The reverse engineering process represents one of the best known methodologies for creating three-dimensional (3D) virtual models starting from physical ones. Even if in the last few years its usage has significantly increased, the remarkable involvement of the operator has until now represented a significant constraint for its growth. Having regard to the fact that this process, and in particular its first step (that is the acquisition phase), strongly depends on the operator's ability and expertise, this paper aims at proposing a strategy for automatically supporting an "optimal" acquisition phase. Moreover, the acquisition phase represents the only moment in which there is a direct contact between the virtual model and the physical model. For this reason, designing an "optimal" acquisition phase will provide as output an efficient set of morphological data, which will turn out to be extremely useful for the following reverse engineering passages (pre-processing, segmentation, fitting, ...). This scenario drives the researcher to use a selective sampling plan, whose grid dimensions are correlated with the complexity of the local surface region analyzed, instead of a constant one. As a consequence, this work proposes a complete operative strategy which, starting from a first raw preliminary acquisition, will provide a new selective sampling plan during the acquisition phase, in order to allow a deeper and more efficient new scansion. The proposed solution does not require the creation of any intermediate model and relies exclusively on the analysis of the metrological performances of the 3D scanner device and of the morphological behaviour of the surface acquired. © 2009 Elsevier B.V. All rights reserved.

Keywords: Free-form , Reverse engineering , Sampling strategy , Scanner uncertainty

Reverse engineering is a technology which generates a virtual representation of an existing part based on point data acquired through measuring techniques. Different technologies can be employed to obtain a virtual representation of a physical model, but the use of a solution (3D scanner) rather than another provides significantly different results since the available 3D scanners are characterised by different performances (resolution, accuracy, ...). However, even if great attention were focussed on the selection of the most appropriate 3D scanner device, this would not be enough to assure the achievement of a consistent virtual representation of the physical model. The selection of the most suitable 3D scanner can contribute to rendering the point acquisition more accurate, but it is not able to assure an efficient point distribution in terms of numbers and locations. These two parameters are part of the acquisition strategy, which can be implemented only after having decided which the 3D scanner is to be used. In order to support the next steps of the reverse engineering cycle (segmentation, fitting, ...), the acquisition phase should provide an organised point cloud, which can be obtained through a consistent sampling plan. For this reason, this paper aims at proposing a methodology for defining a selective sampling plan, whose grid dimensions are related to the complexity of the analysed local surface regions. © 2008 Springer-Verlag London Limited.

Keywords: 3D scanner performances , Free-form , Reverse engineering , Sampling strategy

Many different applications of online product inspections have found a significant advantage by the use of 3D scanners, especially when working with complex surfaces (free-form,), where traditional inspection tools proved to have significant limitations. Unfortunately, there are not only success stories, but also several situations in which the approach towards 3D scanner technologies has been unsuccessful. This is mainly due to the fact that it is hard to understand which 3D scanner solution is the best to adopt and which working protocol is to be followed in order to obtain the best results from a specific application. These problems are often caused by the absence of a long expertise in 3D scanners and by the presence of inappropriate technical sheets. These last are, in fact, quite fragmented and inhomogeneous and only provide little information about the device behavior in the different working scenarios since they tend to be more oriented to the theoretical metrological performances. Most of the time, this information is not useful for users, who need to have a unique map showing both 3D scanner technical performances and their correlations to the different working scenarios in order to be able to compare the several available systems and to get a better understanding of their usage. In order to provide a solution to this problem, this paper proposes to create a customer benchmarking methodology that is a mixture of benchmark geometry designs and experiment sets. This benchmarking methodology will be focused on the simulation of a computer-aided inspection working scenario and carried out by using the quality function deployment method, in order to be oriented towards customer needs. © 2008 Springer-Verlag London Limited.

Keywords: 3D scanner , Laser scanner , Quality function deployment , Reverse engineering

Chronic wounds represent one of the most frequent pathologies affecting elderly people. In the last few years, several methods have been proposed with the aim at developing systems able to produce automatic and objective assessment of skin ulcers. Despite that, none of the existing technologies seems to be robust enough to work for all the ulcer typologies. In the majority of the clinical contexts, the evaluation of chronic wounds still depends on the experience of physicians rather than on the use of numerically objective attributes. This paper presents a non-invasive methodology to allow automatic measurements of chronic wounds. The proposed system involves the development of a 3D optical scanner, based on a structured light approach, combined with an infrared detector. This arrangement permits the acquisition of geometrical data including both chromatic texture and temperature information. A tool for the automatic detection of damaged skin areas has been developed by segmenting both color and thermal images, making possible to reliably quantify parameters characterizing wounds, such as area, depth and volume, even in absence of a perceptible color characterization. The described technology has been finally experienced in medical environment, proving its effectiveness for an objective assessment of wound healing.

Keywords: 3D segmentation , 3D thermography , Imaging , Wound modelling

Reverse Engineering aims at constructing CAD models of existing objects starting from measurement data. In the classical approach a reverse engineering procedure completes in three main steps: data acquisition data processing and modeling. Herein we describe a novel semi-automatic approach for integrating CAD and reverse engineering. The basic idea consists in constructing a parametric and feature-based approximate model and matching it with measurement data to determine the unknown parameters. The approach is semi-automatic since part of the model is constructed manually by the user, while the exact values of the parameters are computed through an optimization procedure based on genetic algorithms. Two case studies are presented and critically discussed.

Keywords: genetic algorithms , geometric modeling , Reverse engineering

The optical methods of contouring are based on a fundamental discipline, Projective Geometry. The 3-D world is projected in 2-D utilizing a camera modeled in the technical literature by a pinhole camera. To get back 3-D information the fundamental property measured is parallax. Parallax is a vector resulting from the difference of the projective coordinates of a point in the space when projected into a plane from two different points. The oldest method used to measure parallax is photogrammetry that at the same time is assumed to be the most precise technique, 10-5 of the largest dimension of the measured object. The paper summarizes the current state of the art of the projection moire method. Starting from the concept of projection moire (PM) as a form of photogrammetry, the different optical techniques for parallax determination are discussed. Although the projection moire method has reached 1 μm accuracy in laboratory work, a question remains: can PM become a standardized contouring technique yielding 10-6 accuracy? The paper is devoted to the analysis of this question, both through theoretical derivations and experimental verifications.

In the current moiré literature, techniques to determine displacements, strains, and techniques to get geometrical parameters of surfaces using the shadow-projection moiré method are considered two separated branches of moiré. We have formulated a mathematical model that shows a deeper commonality between the two moiré applications: strain fields and surfaces are tensors of the second order. A direct consequence of this property is that a system of orthogonal grids is required in both cases when Cartesian tensors are utilized. The two systems of lines projected on a surface to get its contour are assimilated to parametric lines used in differential geometry to describe a surface. The classical moiré equations of projection and observation from infinity are extended to more general conditions of projection and observation. The use of four projectors (i.e., two groups of two projectors) in a mutually orthogonal system with one camera is shown to provide the necessary means to implement the model for high-accuracy contouring. Geometrical primitives are introduced to provide a simple and direct procedure to reduce all the measured values to a preselected coordinate system. Different views of the same surface are merged to the selected coordinate system directly without the need to introduce markers on the surface or utilize correlation methods to identify identical regions. Examples of the application of the new model of contouring to practical cases are presented in the companion paper "A general model for moiré contouring, part 2: applications." © 2008 Society of Photo-Optical Instrumentation Engineers.

Keywords: contouring of surfaces , geometrical primitives , merging of different views , moiré , shadow/projection moiré

Optical Reverse Engineering systems are evermore used to check dimensional and shape conformity of manufactured components; their main advantage is the short acquisition time. Dedicated CAD software tools allow comparing the acquired data (clouds of points) with the 3D CAD model. Generally, they support the automatic global shape measurement; from the designer viewpoint this is not sufficient. The desired functional behavior of component is respected only when specific geometrical tolerances are verified. Our aim is the definition of methods to automate this last control process using Full of Information (FoI) CAD models. We define them as 3D model containing tolerance attributes and methods to check them. They allow comparing the toleranced features with the corresponding parts of point clouds. The present paper describes the approach and the developed method for datum identification usable for orientation and localization geometrical tolerances control. © 2008 CAD Solutions, LLC.

Keywords: Geometrical tolerances , Quality control , Reverse engineering

BACKGROUND: Current methodologies in the prevision of post-surgical features of the face in orthognathic surgery are mainly 2-D. An improvement is certainly given by the introduction of CT, but its acceptance is controversial due to its high biological cost. As an alternative, in this study an effective procedure for the construction of a 3-D textured digital model of the face and dental arches of patients with dentofacial malformations using a 3-D laser scanner at no biological cost is presented. METHODS: A 3-D Laser scanner Konica-Minolta VIVID 910 is used to obtain multiple scans from different perspectives of the face of patients with dentofacial malocclusions requiring orthognathic surgery. These multiple views are then recombined, integrating also the maxillary and mandibular arch plaster casts, to obtain the 3-D textured model of the face and occlusion with minimal error. RESULTS: A viable methodology was identified for the face and occlusal modeling of orthognathic patients and validated in a test case, confirming its effectiveness: the 3-D model created accurately describes the actual features of the patient's face; the proposed methodology can be easily applied in the clinical routine to accurately record the steps of the surgical treatment and to perform accurate anthropometric analyses of the facial morphology, and thus constitute the necessary database for the development of previsional tools in orthognathic surgery. CONCLUSIONS: The proposed method is effective in recording all the morphological facial features of patients with dentofacial malformations, to develop a facial modification database and tools for virtual surgery.

Computed tomography is a medical instrument that can be useful not only for diagnostic purposes, but also for surgical planning, thanks to the fact that it offers volumetric information which can be translated in three dimensional models. These models can be visualized, but also exported to Rapid Prototyping (RP) systems, that can produce these structures thanks to the rapidity and versatility of the technologies involved. The literature reports various cases of stereolithographic models used in orthopedic, neurological, and maxillo-facial surgery. In these contexts, the availability of a copy of the real anatomy allows not only planning, but also the practical execution of surgical operations, within the limitations of the materials. Nevertheless, the Rapid Prototyping model also presents some disadvantages that can be reduced if practical simulation is accompanied by virtual simulation, performed on a digital model. The purpose of this work is to examine and present the use of Virtual Reality (VR) and Rapid Prototyping for surgical planning in Maxillo-Facial surgery. ©2008Muntaz B. Habal, MD.

Keywords: Osteogenesis distraction , Rapid prototyping , Reverse engineering , Surgical planning , Virtual reality

Quality of service, in terms of improvement in patient satisfaction, is an increasingly important objective in all medical fields, and is especially imperative in orthodontics due to the high numbers of patients treated. Information technology can provide a meaningful contribution to bettering treatment processes, and we maintain that systems such as CAD, CAM and CAE, although initially conceived for industrial purposes, should be evaluated, studied and customized with a view to use in medicine. The present study aims to evaluate Reverse Engineering (RE) and Rapid Prototyping (RP) in order to define an ideal chain of advanced technological solutions to support the critical processes of orthodontic activity.

Reverse Engineering is a technology that generates a virtual representation of an existing part based on point data acquisition with measuring techniques. Different technologies could be employed to obtain a virtual representation of a physical model, but the use of a solution (3D scanner) rather than another, could provide significant different results because the available 3D scanners are characterised by different performances (resolution, accuracy,. ..). The selection of the right 3D scanner could guarantee an improvement in the points acquisition precision, but it could not assure an efficient points distribution in term of number and locations. These two parameters make part of the acquisition strategy, that should provide a consistent sampling plan. For this reason this paper wants to propose a methodology to define a selectively sampling plan, with grid dimensions related with the complexity of the local surface region analyzed. © 2008 IEEE.

Keywords: 3D Scanner , Free-Form , Reverse Engineering

The "segmentation", i.e., the three-dimensional point cloud partition in different morphological zones, is a necessary operation while approaching the reverse engineering cycle, because it helps the operator in generating the surface model. This operation is usually developed after the acquisition and the pre-processing phases, and it tries to define a boundary grid which the following surface fitting operation will employ for the surface model definition. Many approaches apply the segmentation methods far from the 3D scanner device. On the contrary, this research proposes an iterative strategy which starts from a first raw point acquisition and then partitions the object surface and identifies the boundary of those zones showing significant morphological features (shape-changes). As a consequence, they will be re-digitised with deeper scansions, in order to reach more precise morphological information. This partitioning operation is driven by a morphology descriptor, the gaussian curvature, giving an estimation of the local surface morphological complexity. Moreover the proposed algorithm employs the 3D scanner measuring uncertainty to define a "curvature variation threshold", in order to identify those zones showing significant morphological shape-changes. © 2006 Springer-Verlag London Limited.

Keywords: Geometric morphology , Reverse engineering , Scanning strategy

The work presented in this paper refers to the implementation of a product development process based on the use of virtual model of the human body to design specific custom-fit product, such as a prosthesis socket (interface between the residual limb and the mechanical part of the prosthesis). It considers the integration of advanced ICT tools coming from the reverse engineering, the physics-based modelling and simulation, and the rapid prototyping fields. The paper describes problems related to the implementation of each step within a real socket development process. © Springer-Verlag Berlin Heidelberg 2007.

Keywords: Human body modeling , Physics-based simulation , Product customization , Prosthesis design

Range maps registration still represents one of the most time consuming phases in the digitization of 3D shapes due to the high user intervention required. The traditional approaches are, in fact, based on manual rough alignments, followed by ICP refining techniques. On the other hand, existing unattended methodologies, based on the automatic searching for correspondent morphological singularities on adjacent point clouds, do not seem to guarantee sufficient robustness and flexibility in the fast reconstruction of target objects. This paper presents a methodology to acquire free-form shapes by combining a 3D stereo vision system and a fully automatic range maps registration process. The automatic alignment is carried out without any assumptions about the initial positions of the point clouds and is based on the automatic detection of fiducial markers, located on the surface object, by processing grey intensity images. © 2008 Taylor & Francis Group.

Shadow (projection moiré) is the oldest form of application of moiré method (1929); papers published in the literature on this subject in the order of hundreds. The multiplicity of papers is a consequence of diverse simplifications used to translate captured images information into the geometry of observed surfaces. Different authors have made different approximations while developing models for moiré contouring fringe data analysis, many times without a thorough evaluation of the adopted simplifications. This make it difficult to evaluate performance of different devices built to measure 3-D shape based on moiré technology. To clarify some of the basic requirements for a successful model, in the 2006 Spring meeting of SEM, a paper was presented proposing a model of moiré contouring based on projective geometry and differential geometry requirements. An application to the determination of the displacements of a large rectangular plate illustrated the proposed model. In this paper the basic ideas presented in the 2006 paper are applied to the contouring of a sample utilized to evaluate the accuracy of laser generated geometrical shapes through the process of laser stereo-lithography. The basic aspects of the process followed to obtain the surface contour are presented and discussed. Comparisons between the optically obtained result, the initial CAD design and a high precision tactile machine are made. These results provide a basis for the evaluation of the obtained result and the feasibility of high precision contouring using moiré contouring techniques. The obtained result show that high precision contouring can be achieved if one applies the correct model that satisfies the basic requirements of projective geometry, differential geometry and the physical optics.

Reverse Engineering and Rapid Prototyping are consolidated practices in the industrial product design process. In any case, best practices should be set up according to the type of product and of objectives. This paper presents the results of a product re-engineering application in the field of high quality stainless steel cutlery. This activity included a re-modeling of a basis-shape that reproduces at best the original shape of a cutlery set designed in the Thirties for Alessi, which is still considered to be very fashionable. The shape of the manufactured physical pieces of cutlery has changed in time in respect to the original design, mainly because of some problems related to their manufacturing, which has been transferred from the central plant to other branches. We have obtained the digital model of the pieces of cutlery on the basis of the analysis of the available original 2D drawings, and of the laser scanning and subsequent re-engineering design of the available manufactured objects. Particularly complex activity was the removal of the shapes deviations due to the different forming techniques used in the various production factories. At the end of the reconstruction activity, physical prototypes of the new models were produced by means of a sintering process in order to evaluate and compare them to the original ones. © The Eurographics Association 2007.

It is well known that the geometrical accuracy is a very relevant problem in Incremental Forming operations, since the material is not well sustained and, then, the elastic springback plays a significant role during the process. A number of researches are involved in the study of geometrical precision after the forming stage but considering the sheet clamped to the equipment. However, it is well known that material coupling is carried out after trimming, when it could change its shape after the new equilibrium. In the paper here addressed the above concept is kept in touch and a wide experimental campaign has been set-up in order to acquire experimental information on the effect of unclamping and trimming after incremental forming processes. The obtained results are able to suggest to the process designer some best practices which are accurately discussed in the paper.

Keywords: Incremental forming , Precision , Sheet metal forming

Purpose: The purpose of this article is the demonstration of virtual reality (VR) and rapid prototyping (RP) in surgical planning in maxillofacial surgery. The authors emphasize the role of reverse engineering (RE) and RP, suggesting a model of cooperative work, with the interaction of maxillofacial surgeons, radiologists, and engineers. Materials and Methods: Data acquisition is performed using computed tomography. The 3D model is the result of RE practices based on image segmentation, and the real model is produced via stereolithography. Virtual simulations are performed on the 3D model obtained from image segmentation. All these stages require the interaction and collaboration of various experts: maxillofacial surgeons, radiologists, and RE and RP experts. Results: VR and stereolithography models represent a new technology to help the surgeon who has to work in cooperation with engineers and radiologists to improve the results in surgical planning of maxillofacial distraction. Conclusion: When performing the VR simulation, surgeons and engineers operate together in order to optimize the exploitation of the instruments available. Both VR and RP, with different and complementary advantages and limitations, can improve surgical planning activities and this is particularly effective when dealing with complex anatomical structures in maxillofacial surgery. © 2007 American Association of Oral and Maxillofacial Surgeons.

In the consumer goods field, the market offers to the customer a wide variety of possible alternatives to satisfy a specific need. Customers, generally, compare products evaluating the functionality and the congruency between price and intrinsic value, but the visual appearance plays a fundamental role in the final decision. During the creative phase, the industrial designer conceives the object in order to represent his/her own viewpoint on the design problem considering the context and the constraints given by the company image. The result of the work of the industrial designer is a set of sketches where curves, notes, shadows, and colours implicitly represent the creative ideas. These signs condense and concretise the design intent that, finally, will be transformed into product visual appearance. During the product development process, various actors are involved and communication problems deriving from the different individual training and experience can emerge. The main consequence is the loss of the original design intent. This is particularly evident in two different design situations: when the designer realizes a physical prototype and Reverse Engineering (RE) is applied to obtain its digital representation for the following product development phases, and when a product is subjected to Re-Styling (RS) in order to satisfy new emerging requirements. Our research is focused on the definition of a well-structured methodology for free form surface reconstruction based on the recognition of the aesthetic features. Such features and their use in surface modelling can enable users to coherently and easily modify the model in the next design stages preserving the design intent. In this paper the CAD modelling operators are defined and their experimentation is applied on several industrial test cases related to reverse engineering and restyling.

Keywords: Aesthetic feature , Communication and collaboration , Design intent , Modelling strategy